Chapter 3 Aerodynamics of Flight Flashcards
What are the 4 forces of flight?
Lift, drag, weight, thrust.
What is the relationship of speed to lift?
lift increases as the speed squared. 2x speed = 4x lift
What are the 2 types of drag?
Parasitic and induced.
Which type of drag increases with airspeed?
Parasitic
Does Induced drag increase or decrease with airspeed?
Induced drag decreases as airspeed increases.
What are the forms of Parasitic drag?
Form - cross section area. Interference - intersection of two forms like vertical and horizontal stabilizers. Skin - due to boundary layer factors laminar to turbulent flow - affected by surface smoothness.
What causes induced drag?
Difference in pressure between the top and bottom of wing which causes votices to form.
Where does max L/D occur?
At the airspeed where induced drag and parasitic drag intersect/
What is aspect ratio?
Length / avg width of wing. Larger aspect ratio will give higher glide ratio. Or wingspan squared / wing area.
What is glide ratio?
Vertical distance fallen / horizontal distance travelled. Measured at best L/D airspeed. Also Sirspeed/ Sink Rate.
What speed do you fly to stay in the air the longest period of time.
Min sink speed.
What speed do you fly to cover the most ground for over a period of time?
Best L/D speed.
What are the 4 wingforms?
ERTS. Elliptical, Rectangular, Tapered, Swept Forward
What is washout?
Twist in wing to cause wing root to stall first (high AOA) before ailerons (low AOA) stall.
Which is lower airspeed, min sink or best L/D?
Min Sink
Does increased weight affect glide ratio?
Glide ratio is not affected by weight. However the airspeed to obtain best L/D will increase.
How is thrust generated in a glider?
Thrust is generated by sinking. PE is converted to KE.
Ailerons control movement around what axis?
Ailerons control movement around the longitudinal axis or Roll.
Rudder controls movement around what axis?
Rudder controls movement around the vertical axis or Yaw.
Elevator controls movement around what axis?
Elevator controls movement around the lateral axis or Pitch
Movement about the vertical axis is called?
Yaw
Pitch is movement around what axis?
Lateral axis
Roll is movement around what axis?
Longitudinal
Too much ailerons without appropriate rudder leads to?
Slips
Not enough ailerons and too much rudder leads to?
Skids
What are characteristics of a skid?
Glider moves to the outside of the turn. Lots of drag.
What are characteristics of a slip?
Glider moves to the inside of a turn and can loose altitude.
What does a glider do in a side slip?
Glider will head straight but will track sideways toward the roll. Will lose altitude.
What does a glider do in a forward slip?
Glider will track straight but head sideways. Will lose altitude without increasing airspeed.
What’s the difference between a side slip and a forward slip?
A forward slip uses much more opposite rudder than a side slip.
When does a stall occur?
A stall occurs when the critical angle of attack is exceeded. Occurs at any airspeed, attitude bank angle
What is the angle of attack (AOA)?
The AOA is the angle between the chord of the wing and the airstream passing over it.
What can increase stall speed?
Increased weight, increased bank, increased AOA, excessive yaw, snow/ice, turbulence
What is a spin?
A spin is an aggravated stall resulting in a descending helical path. Wings are unequally stalled. Stalled wing drops below upper wing and glider yaws in direction of stalled wing. Upper wing has more lift and less drag than lower wing. Occurs in uncoordinated slow flight.
DO NOT practice spins unless recovery can be made 1500’ AGL.
What is spin recovery procedure?
- pitch forward
- stop rotation with rudder.
- gradually pitch back to level flight
Types of spins?
Erect, Inverted, Flat.
At what altitude does ground effect start taking effect?
Below 1 wingspan height above the ground.
What happens to drag during ground effect?
Drag decreases due to reduced downwash over the wings.
What happens to stall speed when in ground effect?
Stall speed decreases because drag is reduced.
What happens to landing distance when in ground effect?
Landing distance increases due to reduced drag.